A problem of the chlor-alkali industries in many countries is the imbalance between the demands for the alkali metal hydroxide and chlorine which are the main products of the electrolysis. It is expected that the balance will get even worse in the future because of the environmental pressure caused by the use of chlorine and its finished products. The result of this is that alternative methods for producing alkali metal hydroxides have to be found, because they can't be produced in adequate quantities by the conventional chlor-alkali electrolysis.
Other known methods for producing alkali metal hydroxides include the following methods:
chemical decarbonation of soda with either lime milk or ammonia, PA1 electrolytical breaking down of an alkali metal sulphate to an alkali metal hydroxide and sulphuric acid, PA1 decarbonation of soda with an acid solution of an alkali metal sulphate and the electrolysis of so obtained sulphate solution to an alkali metal hydroxide, PA1 catalytical breaking down of an alkali metal sulphide to an alkali metal hydroxide and sulphur dioxide and PA1 electrolytical breaking down of an alkali metal chlorate to an alkali metal hydroxide and chlorine dioxide.
The chlorate is generally produced by electrical breaking down of alkali metal chlorides.
All of these known methods are unfavorable for the present producers of alkali metal hydroxide. The disadvantages of the most common alternative processes are the following: too much of sulphur compounds are produced as by-products in the process, having no use in a large scale; the raw material and energy costs of the process are too high compared to the market price of the product; big investments are required in the process and thus its capital costs are getting unfavorable in proportion to the market price of the product.